fix(modbus): gate array read on isArray:true; 1-element arrays (review C-1)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts/ModbusEquipmentTagParser.cs

@@ -35,9 +35,13 @@ public static class ModbusEquipmentTagParser
             var bitIndex = (byte)ReadInt(root, "bitIndex");
             var stringLength = (ushort)ReadInt(root, "stringLength");
             // isArray / arrayLength — optional keys authored by the typed Modbus tag editor.
-            // When arrayLength > 0 we expose an array tag of that count; otherwise scalar.
+            // Canonical rule: a tag is an array iff isArray:true AND arrayLength >= 1.
+            // isArray:false (with any arrayLength) is scalar — the foundation materialises a
+            // scalar OPC UA node, so returning an array value would cause a shape mismatch.
+            // A 1-element array (isArray:true, arrayLength:1) IS valid and reads as short[1].
+            var isArray = ReadBool(root, "isArray");
             var arrayLength = ReadInt(root, "arrayLength");
-            int? arrayCount = arrayLength > 0 ? arrayLength : null;
+            int? arrayCount = (isArray && arrayLength >= 1) ? arrayLength : null;
             def = new ModbusTagDefinition(
                 Name: reference, Region: region, Address: (ushort)address, DataType: dataType,
                 Writable: true, ByteOrder: byteOrder, BitIndex: bitIndex, StringLength: stringLength,
@@ -56,4 +60,7 @@ public static class ModbusEquipmentTagParser
     private static int ReadInt(JsonElement o, string name)
         => o.TryGetProperty(name, out var e) && e.ValueKind == JsonValueKind.Number
            && e.TryGetInt32(out var v) ? v : 0;
+
+    private static bool ReadBool(JsonElement o, string name)
+        => o.TryGetProperty(name, out var e) && e.ValueKind == JsonValueKind.True;
 }